Researchers uncover a circuit for sadness in the human brain

Patients awaiting epilepsy surgery agreed to keep a running log of their mood while researchers used tiny wires to monitor electrical activity in their brains. The combination revealed a circuit for sadness.

Human brain networks that encode variation in the mood on naturalistic timescales remain largely unexplored. In a new study, scientists combined multi-site, semi-chronic, intracranial electroencephalography recordings from the human limbic system with machine learning methods to discover a brain subnetwork that correlates with variation in individual subjects’ self-reported mood over days.

Scientists at the University of California, San Francisco reported that they may have discovered a glimpse of what sadness looks like in the brain. The study is expected to pave the way for better understanding of mood disorders, and perhaps new ways of treating them.

Scientists identified 21 people and found that for most, feeling down was related with more prominent correspondence between brain areas associated with emotion and memory.

Vikaas Sohal, an associate professor of psychiatry at UCSF said, “There was one network that over and over would tell us whether they were feeling happy or sad.”

Scientists can not able to get that information from brain scans, which don’t capture changes that happen in fractions of a second. So the team studied 21 people who were in the hospital awaiting brain surgery for severe epilepsy.

Before the surgery, doctors insert tiny wires into the brain and monitor its electrical activity for up to a week. Scientists expect that the recordings would help answer a basic question: When patients are sitting there, or watching TV or talking with their family or waiting or being anxious, which regions of the brain are talking to each other?

The patients agreed to keep a running log of their mood. And the team looked to see whether certain moods coincided with communication within specific networks in the brain. The researchers thought they might find networks that were similar in a couple of people. But they were “really surprised” to learn that 13 of the 21 patients shared the same network.

“Still, it makes sense that communication between areas involved in memory and emotion would be associated with sadness. Maybe you’re feeling down and so you start remembering times in your life when bad things have happened, or you are starting to remember those experiences and that is what is making you feel down.”

“As a psychiatrist, it’s incredibly powerful to just be able to say to patients, ‘Hey, I know there’s something happening in your brain when you’re feeling down.'”

Dr. Joshua Gordon, who directs the National Institute of Mental Health said, “It’s finding a circuit, a piece of the brain that we kind of already knew was involved in the mood — that’s the less-than-wow part. The wow part is that it’s in human beings.”

“The study also provides a detailed map of what’s going on in the human brain, which is what doctors and scientists need to look for better treatments for patients with mood disorders.”

“It’s really important that we find the circuits underlying mood so we can learn more about them and treat them with tools we are developing that are aimed at circuits. Those tools include transcranial magnetic stimulation, which uses pulses of energy delivered through the skull to change the activity of brain circuits.”

The study also shows the value of the BRAIN Initiative, which was launched by then-President Obama in 2013.